Phononic travelling wave gyroscope

Abstract

A phononic travelling wave gyroscope. The gyroscope includes a phononic waveguide including at least one loop. The phase change incurred by phonons propagating around the loop is compared to a reference phase, and utilized to form an estimate of the rotational rate of the gyroscope.

What is claimed is: 
     
       1. A gyroscope, comprising:
 a first phononic waveguide comprising a first loop for guiding first phonons; 
 a first phonon generator operatively coupled to the first phononic waveguide; 
 
       a first phonon detector operatively coupled to the first phononic waveguide;
 a second phononic waveguide comprising a second loop for guiding second phonons; 
 a second phonon generator operatively coupled to the second phononic waveguide, 
 wherein a phase of the second phonons after traveling at least once around at least the second loop in a second direction opposite the first direction is a reference phase; 
 a phononic waveguide coupler having: 
 a first input connected to an output end of the first phononic waveguide; 
 a second input connected to an output end of the second phononic waveguide; and 
 a first output connected to the first phonon detector; and 
 a circuit configured to estimate, from a phonon power received by the first phonon detector, a phase difference between: 
 a phase of the first phonons received by the first input of the coupler, after traveling at least once around at least the first loop in the first direction, and 
 the reference phase of the second phonons received by the second input of the coupler. 
 
     
     
       2. The gyroscope of  claim 1 , further comprising:
 a second phonon detector operatively coupled to the second phononic waveguide, 
 wherein: 
 the phononic waveguide coupler further has a second output connected to the second phonon detector, and 
 the circuit is configured to estimate a phase difference between 
 the first phonons received by the first input of the coupler, and 
 the second phonons received by the second input of the coupler from: 
 the phonon power received by the first phonon detector and/or 
 a second phonon power received by the second phonon detector. 
 
     
     
       3. The gyroscope of  claim 1 , wherein the circuit is configured to drive the first phonon generator with a first drive signal and to drive the second phonon generator with the first drive signal. 
     
     
       4. The gyroscope of  claim 1 , wherein the first phonon generator comprises a first electrode and a second electrode,
 the first electrode and the second electrode being configured to experience a mutually attractive force in response to a voltage applied across them, and 
 the first electrode and the second electrode being both mechanically coupled to the first phononic waveguide and configured to transmit phonons into the first phononic waveguide when an oscillating voltage is applied across them. 
 
     
     
       5. The gyroscope of  claim 1 , wherein the first phonon detector comprises a first electrode and a second electrode,
 the first electrode and the second electrode being mechanically coupled to the first phononic waveguide and configured to form a capacitor having a capacitance that fluctuates when phonons propagate into the first phonon detector. 
 
     
     
       6. The gyroscope of  claim 1 , wherein the first phonon detector comprises an opto-mechanical cavity configured to act as a phonon resonator and as a photon resonator, the opto-mechanical cavity being operatively coupled to the first phononic waveguide and to a photonic waveguide. 
     
     
       7. The gyroscope of  claim 1 , wherein the first phonon generator comprises a piezoelectric element configured to transmit phonons into the first phononic waveguide. 
     
     
       8. The gyroscope of  claim 1 , wherein the first phonon detector comprises a piezoelectric element configured to receive phonons from the first phononic waveguide. 
     
     
       9. The gyroscope of  claim 1 , wherein the first phonon generator comprises a thermal actuator configured to expand when heated by an electric current or by light, and configured to transmit phonons into the first phononic waveguide. 
     
     
       10. The gyroscope of  claim 1 , wherein the first phonon detector comprises a thermal element configured to receive and absorb phonons from the first phononic waveguide and to exhibit a change in temperature in response to an absorption of phonons. 
     
     
       11. The gyroscope of  claim 1 , wherein the first phononic waveguide is a curved suspended structure, having a rectangular cross section with dimensions of less than 10 microns by 10 microns. 
     
     
       12. The gyroscope of  claim 1 , wherein the first phononic waveguide is a phononic crystal waveguide. 
     
     
       13. A gyroscope, comprising:
 a first phononic waveguide comprising a first loop, 
 wherein the first phononic waveguide is a phononic crystal waveguide; 
 a first phonon generator operatively coupled to the first phononic waveguide; 
 a first phonon detector operatively coupled to the first phononic waveguide; and 
 a circuit configured to estimate a difference between: 
 a phase of phonons, after traveling at least once around at least the first loop in a first direction, and 
 a reference phase, 
 the gyroscope further comprising; 
 a substrate; 
 an anchor layer comprising a plurality of anchors; and 
 an acoustic layer supported by the anchors, 
 the acoustic layer having a first plurality of holes arranged in a periodic structure forming a phononic bandgap, 
 the first phononic waveguide being defined on the acoustic layer by a path lacking holes or having holes differing, in size or in spacing, from the holes of the first plurality of holes. 
 
     
     
       14. The gyroscope of  claim 13 , further comprising:
 a second phononic waveguide comprising a second loop; 
 a second phonon generator operatively coupled to the second phononic waveguide; and 
 wherein the reference phase is a phase of phonons after traveling at least once around at least the second loop in a second direction opposite the first direction. 
 
     
     
       15. The gyroscope of  claim 13 , further comprising:
 a second phonon generator; 
 a second phonon detector; 
 a first phononic waveguide coupler having: 
 a common port connected to a first end of the first phononic waveguide; 
 an input port connected to the first phonon generator and coupled to the common port; and 
 an output port connected to the first phonon detector, the output port being coupled to the common port and isolated from the input port; and 
 a second phononic waveguide coupler having: 
 a common port connected to a second end of the first phononic waveguide; 
 an input port connected to the second phonon generator and coupled to the common port; and 
 an output port connected to the second phonon detector, the output port being coupled to the common port and isolated from the input port, wherein the circuit is configured: 
 to drive the first phonon generator with a first drive signal and to drive the second phonon generator with the first drive signal; and 
 to estimate a difference between: 
 a phase of phonons detected by the first phonon detector, and 
 a phase of phonons detected by the second phonon detector. 
 
     
     
       16. The gyroscope of  claim 13 , wherein the first phonon generator comprises a first electrode and a second electrode,
 the first electrode and the second electrode being configured to experience a mutually attractive force in response to a voltage applied across them, and 
 the first electrode and the second electrode being both mechanically coupled to the first phononic waveguide and configured to transmit phonons into the first phononic waveguide when oscillating voltage is applied across them. 
 
     
     
       17. The gyroscope of  claim 13 , wherein the first phonon detector comprises a first electrode and a second electrode,
 the first electrode and the second electrode being mechanically coupled to the first phononic waveguide and configured to form a capacitor having a capacitance that fluctuates when phonons propagate into the first phonon detector. 
 
     
     
       18. The gyroscope of  claim 13 , wherein the first phonon detector comprises an opto-mechanical cavity configured to act as a phonon resonator and as a photon resonator, the opto-mechanical cavity being operatively coupled to the first phononic waveguide and to a photonic waveguide. 
     
     
       19. The gyroscope of  claim 13 , wherein the first phonon generator comprises a piezoelectric element configured to transmit phonons into the first phononic waveguide. 
     
     
       20. The gyroscope of  claim 13 , wherein the first phonon detector comprises a piezoelectric element configured to receive phonons from the first phononic waveguide. 
     
     
       21. The gyroscope of  claim 13 , wherein the first phonon generator comprises a thermal actuator configured to expand when heated by an electric current or by light, and configured to transmit phonons into the first phononic waveguide. 
     
     
       22. The gyroscope of  claim 13 , wherein the first phonon detector comprises a thermal element configured to receive and absorb phonons from the first phononic waveguide and to exhibit a change in temperature in response to an absorption of phonons. 
     
     
       23. The gyroscope of  claim 13 , wherein the first phononic waveguide is a curved suspended structure, having a rectangular cross section with dimensions of less than 10 microns by 10 microns. 
     
     
       24. The gyroscope of  claim 13 , wherein the first phononic waveguide is a phononic crystal waveguide.